chore: enable buildifier formatting check

[alexeagle]

It literally took me two hours to get all the hyphens in the right spots to make it remain formatted along every conditional path.

Note that I could update to a newer scaffold that has a "post" hook feature, but then every user will observe that format running after stamping it out, so this is better (even if really annoying)

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Changes are visible to end-users: no

Test plan

• Covered by existing test cases

[mattem]

so this is better

maybe, This requires a high level of effort to maintain, something that I reckon will slip quickly (a fly by contributor is unlikely to spend the 2 hours getting this right), so I think we need to figure the post process out, and hide the output or something.

[alexeagle]

Yeah I agree. I spent nearly one hour of that on a single pathological location (top of the root BUILD) and eventually learned a technique that helps (de-sugar the hyphens until you have it right). So we'll see...